Hydrogel wound dressing and the method of making and using the same

ABSTRACT

A hydrogel wound dressing which is highly absorptive, contours to a wound site, and maintains the wound in a moist state to promote healing thereof. The hydrogel wound dressing may also contain additives to prevent bacterial and fungal infections and to control wound odor.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This Patent Application is a Continuation-In-Part of U.S.application Ser. No. 09/156,547 filed Sep. 17, 1998, now U.S. Pat. No.6,180,132, the contents of which are incorporated herein by reference inits entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to a hydrogel wound dressing and amethod of making and using the same. More particularly, the presentinvention relates to a flexible hydrogel wound dressing which is highlyabsorptive, contours to a wound site and maintains a wound in a moiststate to promote healing thereof and the method of producing and usingthe same. The hydrogel wound dressing may also contain additives such asantibiotics and/or anti-fungals, and/or other organic compounds toprevent infection and to control odor.

BACKGROUND OF THE INVENTION

[0003] The treatment of draining wounds is a problem in the medicalprofession. Wound exudate such as blood, serum and purulent matter froma draining wound can lead to bacterial growth and delayed healing if nottreated properly. Difficulties arise in maintaining wounds free of suchwound secretions to allow for healing. Another concern in treating suchdraining wounds is that some believe that allowing a wound to heal in aslightly moist state may actually accelerate healing. Accordingly, themedical profession desires a means for maintaining draining wounds in aclean, moist protected state.

[0004] Currently, in an attempt to meet such wound treatment needs,there are wound exudate absorption compositions which are comprised ofhydrogel materials in powder form. One example of such a powder materialincludes dextranomer beads. Dextranomer beads are hydrophilic sphericalbeads which are applied to a wound to absorb wound exudate.Disadvantages noted in using materials in powder form include difficultyin achieving even application, lumping and clumping of the materialafter application removing the material from a wound site withoutdamaging newly formed tissues in the wound.

[0005] U.S. Pat. No. 4,226,232 discloses the blending of a hydrogelmaterial with a liquid curing agent such as polyethylene glycol prior tointroducing the material to a wound. A difficulty observed in the use ofthis material is that it can not be sterilized by irradiation due to theformation of free radicals within the gel material. These free radicalsso formed within the gel material cause an instability of the hydrogelproduct thereby shortening the shelf life thereof.

[0006] U.S. Pat. No. 5,059,424 (“'424 patent”) discloses a wounddressing comprising a backing member with an adhesive layer and ahydrogel material layer of 15-30% polyhydric alcohol, 8-14% isophoronediisocyanate prepolymer, 5-10% polyethylene oxide-based diamine, 0-1%salt and the balance water. Difficulties associated with the use of thiswound product include the limitation of not being able to cut thedressing to a size appropriate for the particular wound site and stillhaving the backing member intact. Additionally, the hydrogel materialdisclosed in the '424 patent lacks the necessary strength to be used andremoved intact without the added support of the backing material.

[0007] The need exists for a sterile wound dressing which provides asize appropriate protective covering for a draining wound capable ofabsorbing exudate from the wound. It is also desirable to have a wounddressing suitable to protect a wound from debris and foreign mattercapable of contaminating the wound. It is also desirable to have a wounddressing which cushions a wound from pressure. It is also desirable tohave a wound dressing which does not adhere to new tissue forming in awound. It is also desirable to have a wound dressing which maintains awound in a slightly moist state to promote healing. It is also desirableto have a wound dressing which will prevent the occurrence of infection.It is also desirable to have a wound dressing which will maintain awound in a moist state without promoting a fungal infection. It is alsodesirable to have a wound dressing which will aid in the elimination ofwound odor.

SUMMARY OF THE INVENTION

[0008] An illustrative embodiment of the present invention relates to atransparent, insoluble hydrogel wound dressing capable of absorbingexudate from a draining wound without becoming adhered thereto. Thesubject wound dressing maintains a wound in a slightly moist state topromote healing of the wound while retaining its overall strength toallow for removal thereof in a unitary fashion.

[0009] The hydrogel wound dressing of the illustrative embodiment is apolyurethane hydrogel material comprising polyurethane prepolymer,deionized water, glycols, polyalkyldiamine and optionally an anti-fungaland/or an antimicrobial and/or a bacteriostatic agent, and/or an organicadditives may be added.

[0010] The method of producing the hydrogel material of the illustrativeembodiment involves hydrolysis and addition reactions to produce athree-dimensional cross-linked polyurethane hydrogel as described inmore detail below. The resultant polyurethane hydrogel material isblended and cast molded to allow for complete gelatinization thereof inless than 180 minutes at room temperature. Gelatinization preferablybegins within 30 to 40 minutes. The subject bubble-free hydrogel wounddressing is then optionally subjected to temperatures below 0° C. toremove excess water prior to packaging and sterilization using radiationsterilization or other suitable sterilization techniques known to thoseskilled in the art prior to distribution.

[0011] The hydrogel material of the illustrative embodiment mayoptionally contain a variety of additives such as antibiotic compounds.The inert properties of the hydrogel prevent any such additive frombeing released from the hydrogel. Additives such as antibacterialcompounds are not released from the hydrogel and are only effective uponcontact for the efficacious properties of the additives. The hydrogelmay also contain various anti-fungal agents to prevent the occurrence offungal infection while still maintaining a desirable moist environment.Additionally, the hydrogel may also contain organic additives for theadded benefit of controlling wound odor.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The polyurethane hydrogel wound dressing of the illustrativeembodiment is capable of absorbing moisture from a wound site or otherbodily fluids discharged from the body until the overall compositioncomprises approximately 70 percent to 99 percent water or fluid. Thesubject non-adhesive hydrogel dressing provides for moist wound healing,absorbs wound exudate, allows for relatively fewer dressing changes,allows for easy removal with no trauma to a wound, protects a wound fromcontamination and minimizes wound odor.

[0013] The polyurethane hydrogel material of the illustrative embodimentis generally produced by the formation of carbamate (urethane) linkagesby the reaction of isocyanates with alcohols and by the formation ofurea linkages through the reaction of isocyanates with water. Thesereactions are achieved by blending a polyoxyethylene-rich isophoronediisocyanate terminated oligomer, i.e., a polyurethane prepolymer, witha polyetherdiamine chain modifier having a predominately polyethyleneoxide backbone and an approximate molecular weight between 500 and5,000, deionized water, propylene glycol and polyethylene glycol inaccordance with the following reactions:

[0014] STEP 1

[0015] O═C—N—R¹—N═C═O+2R²OH→R2 OOC—HN—R^(1—)NH—COOR²+O═C—N—R¹—N═C═O

[0016] Prepolymer+Alcohol→Polyurethane+Unreacted Prepolymer

[0017] STEP 2

[0018] R¹—NH—COOR²+O═C═N—R¹ 13N═C═O+2H₂O+R¹ONH₂→R¹NH₂+2CO₂+O═C═N—R¹—N═C═O+R¹—NH—COOR²

[0019] Polyurethane+Unreacted Prepolymer+Water+AmineAccelerator→Polyamine(unstable intermediate)+Carbon Dioxide+UnreactedPrepolymer+Polyurethane

[0020] STEP 3

[0021] R¹—NH—COOR²+C═N—R¹—N═C═O+2R¹NH₂→R¹HNOC—HN—R¹NH—CONHR¹+R¹—NH—COOR²

[0022] Polyurethane+Unreacted Prepolymer→Polyurea(stable)+Polyurethane+Polyamine (unstable intermediate}

[0023] Wherein the R¹ groups may be the same or different selected fromthe group consisting of C₁₋₁₂ alkyl repeating groups such as for examplemethyl, ethyl or propyl but preferably propyl for increased strength andstability; C₁₋₁₂ mono-or poly-hydroxyalkyl repeating groups such as forexample hydroxymethyl or dihydroxypropyl but preferably dihydroxypropylfor increased strength and stability; C₁₋₁₂ acyl repeating groups suchas for example acetyl or proprionyl but preferably proprionyl forincreased strength and stability; C₁₋₁₂ alkoxyalkyl repeating groupssuch as for example methoxyethyl or ethoxypropyl but preferablyethoxypropyl for increased strength and stability; C₁₋₁₂ aminoalkylrepeating groups such as for example aminomethyl or aminopropyl butpreferably aminopropyl for increased strength and stability; C₁₋₁₂acylaminoalkyl repeating groups such as for example acetylaminomethyl orproprionylaminomethyl but preferably prorionylaminomethyl for increasedstrength and stability; C₁₋₁₂ oxyalkyl repeating groups such as but notlimited to oxyethylene oxypropylene or oxybutylene but preferablyoxyethylene and/or oxypropylene to increase clarity, such repeatingunits having an average molecular weight of about 7,000 to about 30,000capped with aromatic, aliphatic or cycloaliphatic isocyanates,diisocyanates or polyisocyanates, but most preferably diisocyanate- orpolyisocyanate-capped repeating units as described above havingmolecular weights of at least 10,000.

[0024] The use of aliphatic polyisocyanates is preferred in theillustrative embodiment to achieve a greater degree of handling freedomsince aliphatic isocyanate-capped prepolymers typically require longerperiods of time for gelatinization. In addition, aliphaticpolyisocyanates will be preferred when the material is intended to beused in medical applications, because of increased biocompatability anddecreased toxicological considerations. By contrast, prepolymers cappedwith aromatic polyisocyanates gelatinize in about 30 to 60 seconds asopposed to 20 to 90 minutes as typical for aliphatic isocyantes.Gelatinization within 30 to 60 seconds is a disadvantage for use in thepresent application due to a lack of adequate time for proper blendingof the materials and molding thereof. The subject reaction mixture formsa hydrogel in approximately 15 to 180 minutes at room temperature butpreferably in approximately 15 to 90 minutes. Gelatinization can also beaccelerated if desired with the use of a standard curing oven. Apreferred method of accelerating gelatinization has been found toinclude heating the composition at approximately 30 to 80 degreesCelsius for 5 to 40 minutes but more preferably at approximately 45degrees Celsius for 30 minutes.

[0025] Examples of suitable dysfunctional and polyfunctional isocyanatesinclude but are not limited to isophorone diisocyanate,toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, mixtures oftoluene-2,4, and 2,6-diisocyanate, ethylene diisocyanate, ethylidenediisocyanate, propylene-1,2-diisocyanate,cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate,m-phenylene diisocyanate, 3,3′-diphenyl-4,4′-biphenylene diisocyanate,4,4′-biphenylene diisocyanate, 4,4′-diphenylmethane diisocyanate,3,3′-dichloro-4,4′-biphenylene diisocyanate, 1,6-hexamethylenediisocyanate, 1,4-tetramethylene diisocyanate, 1,10, decamethylenediisocyanate, cumene-2,4-diisocyanate, 1,5-naphthalene diisocyanate,methylene dicyclohexyl diisocyanate, 1,4-cyclohexylene diisocyanate,p-tetramethyl xylylene diisocyanate, p-phenylenediisocyanate,4-methoxy-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylenediisocyanate, 4-bromo-1,3-phenylene diisocyanate, 4-ethoxy-1,3-phenylenediisocyanate, 2,4-dimethylene-1,3-phenylene diisocyanate,5,6-dimethyl-1,3-phenylene diisocyanate, 2,4-diisocyanatodiphenylether,4,4′-diisocyanatodiphenylether, benzidine diisocyanate,4,6-dimethyl-1,3-phenylene diisocyanate, 9,10-anthracene diisocyanate,4,4′-diisocyanatodibenzyl,3,3′-dimethyl-4,4′-diisocyanatodiphenylmethane,2,6-dimethyl-4,4′-diisocyanatodiphenyl, 2,4-diisocyanatostilbene,3,3′-dimethoxy-4,4′-diisocyanatodiphenyl, 1,4-anthracenediisocyanate,2,5-fluorenediisocyanate, 1,8-naphthalene diisocyanate,2,6-diisocyanatobenzfuran, 2,4,6-toluene triisocyanate,p,p′,p″-triphenylmethane triisocyanate, trifunctional trimer ofisophorone diisocyanate, trifunctional biuret ofhexamethylenediisocyanate, trifunctional trimer of hexamethylenediisocyanate and polymeric 4,4′-diphenylmethane diisocyanate, butpreferably diisophorone diisocyanate or isophorone diisocyanate for apreferred rate of gelatinization. Isophorone diisocyanate is utilizedwithin the illustrative embodiment as a polyurethane pre-polymer becauseof its ability to completely react therefore leaving no unreacted IPDIgroups. The absence of unreacted IPDI groups renders the hydrogeldressing inert. This inert nature of the hydrogel dressing prohibits therelease of additive agents contained within the dressing preventing thesystematic absorption of the additive agents.

[0026] R²OH is selected from the group consisting of C₁₋₁₂ monohydricalcohols such as ethanol, methanol or propanol, but preferably ethanolfor improved biocompatability, C₁₋₁₂ diols such as alkyl glycols andderivatives thereof wherein propylene glycol is preferred for improvedbiocompatability, and C-₁₋₁₂ polyalkyldiols such as polypropyleneglycol, polyethylene glycol or polybutylene glycol wherein polyethyleneglycol is preferred for better biocompatibility. Most preferably,propylene glycol and/or polyethylene glycol is used in the illustrativeembodiment for biocompatability. Additionally, R² represents thecorresponding C₁₋₁₂ alkyl group, such as methyl, ethyl or propyl butmost preferably methyl for improved stability, C₁₋₁₂ hydroxyalkyl groupsuch as hydroxy methyl hydroxyethyl or hydrooxypropyl but mostpreferably hydroxy methyl for improved stability, or C₁₋₁₂polyhydroxyalkyl group derived from R²OH such as polyhydroxymethyl,polyhydroxyethyl, and polyhydroxypropyl but preferably polyhydroxymethylfor improved stability. The resultant clear or transparent product ofthe subject invention allows for undisturbed viewing of a wound forbetter wound care management.

[0027] The above noted chemical reactions illustrate the process bywhich the subject hydrogel is produced. In the initial step, asillustrated in STEP 1, an alcohol is reacted with a polyurethaneprepolymer such as a isophorone diisocyate prepolymer but preferably aprepolymer of the following chemical composition:

[0028] Wherein the R³ groups may be the same or different selected fromthe group consisting of hydrogen and C₁₋₁₀ alkyl group such as forexample methyl or ethyl but preferably methyl for improved stability;and n represents integers which may differ from one another within therange of 1 to 200. A mixture of hydrogen and methyl groups are thepreferred R³ groups for the above-described prepolymer in order toincrease the flexibility and hydrophilicity of the final hydrogelproduct. The prepolymer is reacted with a C₁₋₁₂ alcohol, C₁₋₁₂ diol,C₁₋₁₂ alkyldiol and/or C₁₋₁₂ polyalkyldiol as described above, such aspolyethylene glycol or propylene glycol in an alcoholsis reaction toform a polyurethane. Next, as illustrated in STEP 2 unreacted prepolymerfurther reacts with water and the polyalkoxyamine accelerator to undergoa hydrolysis reaction to form a polyamine and carbon dioxide. Due to thefact that the polyamine produced in STEP 2, is an unstable intermediatein this reaction process, STEP 3 illustrates the continued reaction ofthe polyamine of STEP 2, undergoing an addition reaction to form astable polyurea. The rate of gelatinization for the polyurea isincreased through the addition of the accelerator. Suitable acceleratorsinclude sodium carbonate, carbonate salts, sodium hydroxide, sodiumcitrate, potassium phosphate, ammonia, and polyalkoxyamines such as butnot limited to polyetheramine due to its solubility and gelatinizationacceleration capability. It has been found that such accelerators whichare water soluble and have a molecular weight of preferably 200 to 5,000improve polymerization rates. The series of reactions just describedrather than producing a foam, results in a three-dimensionalcross-linked polyurethane/polyurea hydrogel. It is important to notethat water is added at the end of the second step of the procedure inorder to prevent premature gelatinization and foaming. Additionally, thepercentage of free isocyanate present in the prepolymer directly affectsthe gelatinization reaction rate. For this reason, in the illustrativeembodiment the percentage of free isocyanate present in the reactionmixture is strictly controlled to a level below 5 percent to slow thereaction and slow gelatinization. Another consideration to be noted isthat the faster the reaction rate, the faster the carbon dioxide gas isproduced, which if not properly controlled causes the formation of afoam rather than a hydrogel. It is the control of these criticalfactors, i.e., the percentage of isocyanate present, the reaction rateand the gelatinization rate among the other considerations noted herein,which allows one to produce the unexpectedly superior hydrogel of theillustrative embodiment.

[0029] In order for one to achieve the desired reaction mixture of theillustrative embodiment and form a hydrogel of desirable strength andintegrity for the intended use, STEP 1 involves blending togetherapproximately 25 to 70 percent of the polyurethane prepolymer butpreferably approximately 60.5 percent and approximately 30 to 75 percentof a polyalkyl diol such as polyethylene glycol but preferablyapproximately 39.5 percent to produce Product A. STEP 2 involvescombining approximately 50 to 90 percent deionized water but mostpreferably approximately 74.2 percent, approximately 0.2 to 10 percentof a polyaikoxyamine such as polyetheramine but preferably about 1.6percent to reduce production time by increasing the rate ofgelatinization, and approximately 5 to 40 percent of an alkyl diol suchas propylene glycol but preferably about 24.2 percent to produce ProductB to react with Product A. Approximately 15 to 60 percent of Product Abut preferably about 38.0 is blended with approximately 40 to 85 percentof Product B but preferably about 62.0 percent to produce the desiredhydrogel wound dressing of the illustrative embodiment.

[0030] Optionally, 0-5% but preferably 1-3% of an antimicrobial or abacteriostatic agent can be added to the final reaction mixture orProduct B. Suitable such antimicrobial and bacteriostatic agents includebut are not limited to: the biguanides, especially chlorhexidine and itssalts, including chorhexidene acetate, chlorhexideine gluconate,chlorhexidine hydrochloride, and chlorhexidine sulfate, silver and itssalts, including silver acetate, silver benzoate, silvercarbonate,silver iodate, silver iodide, silver lactate, silver laurate, silvernitrate, silver oxide, silver palmitate, silver protein, and silversulfadiazine, polymyxin, tetracycline, aminoglycosides, such astobramycin and gentamicin, rifampician, bacitracin, neomycin,chloramphenical, quinolone such as oxolinic acid, norfloxacin, nalidixacid, pefloxacin, enoxacin and ciprofloxacin, penicillins such asampicillin, amoxicillin and piracil, cephalosporins, vancomycin, bismuthtribromophenate, and combinations of any of the above anti-microbials.These anti-microbial agents can be incorporated singularly or incombination or in combination with other additives.

[0031] Optionally, 0-5% but preferably 1-3% of an anti-fungal agent canbe added to the final reaction mixture or Product B. Suitableanti-fungal agents include but are not limited to: Tolnaftate,Miconazole, Fluconazole, Econazole, Ketoconazole, Itraconazole,Terbinafine, and Polyene antifungal agents such as Amphotericin,Nystatin and Natamycin. These anti-fungal agents can be incorporatedsingularly or in combination with other additives.

[0032] Optionally, 0-5% but preferably 1-3% of an organic compounds canbe added to the final reaction mixture or Product B. Suitable suchorganic compounds include but are not limited to: Grapefruit SeedExtract, Tea Tree Oil, Myrtle Oil, and Lemon grass extract. Theseorganic compounds can be incorporated singularly or in combination withother additives

[0033] In one illustrative embodiment bismuth tribromophenate or silversulfadiazine are optionally added to the reaction mixture to decreasethe risk of wound infection and odor. The resultant hydrogel wounddressing is characterized in that it comprises 5 to 30 percent by weightof a polyurethane prepolymer but most preferably 23 percent, 3 to 45percent by weight of polyethylene glycols and propylene glycols but mostpreferably 30 percent and the balance water, accelerator and optionaladditives. The polyurethane hydrogel of the present invention ismanufactured as further described in the following examples:

EXAMPLE A Hydrogel Produced From Isophorone Diisocyanate BasedPrepolymer

[0034] Ten grams of isophorone diisocyanate prepolymer was mixedthoroughly with 10.0 grams of polyethylene glycol (Portion A). Then 30.0grams of deionized water was mixed with 10.0 grams of propylene glycoland 0.5 grams of polyetherdiamine (Portion B). Portion A and Portion Bwere mixed thoroughly with a stirring rod for about two to 5 minutesuntil a homogeneous solution was formed. The solution was then cast intoa 4″×4″ mold coated with a silicone-polyethylene oxide polymer releaseagent and maintained undisturbed for 90 minutes at room temperaturewhile the gelatinization reaction occurred. The mold was kept in aclosed container at room temperature overnight to prevent waterevaporation and to permit essentially complete chemical reaction of allisocyanate end groups. The final hydrogel upon removal from the mold wasflexible, transparent and able to absorb 40 to 50 percent its own weightin one hour.

EXAMPLE B Hydrogel Produced From Toluene Diisocyanate Based Prepolymer

[0035] Five grams of polyethylene glycol was mixed with five grams oftoluene diisocyanate prepolymer (Portion A). Then fifteen grams ofdeionized water was mixed with seven grams of propylene glycol and 0.7grams of polyetherdiamine (Portion B). Portion A and Portion B werequickly mixed and cast into two aluminum weighing dishes coated withsilicone-polyethylene oxide copolymer release agent. The materialgelatinized within 30 minutes. Both dishes, filled with the hydrogelmaterial, were kept in a closed container at room temperature overnightto prevent water evaporation and to permit essentially complete chemicalreaction of all isocyanate end groups. The final hydrogel material, uponremoval from the dishes, was flexible, transparent and able to absorb 40to 50 percent its own weight in one hour.

EXAMPLE C Hydrogel Produced With Bacteriostatic Agent BismuthTribromophenate (BTP)

[0036] A hydrogel with BTP was formed by repeating the preparation ofExample A, except 0.6 grams of BTP was added to Portion B. The finalhydrogel was flexible and able to absorb 40 to 50 percent its own weightin one hour.

EXAMPLE D Hydrogel Produced With Antimicrobial Silver Sulfadiazine (SSD)

[0037] A hydrogel with SSD was formed by repeating the preparation ofExample A, except 0.2 grams of SSD was added to Portion B. The finalhydrogel was flexible and able to absorb 40 to 50 percent its own weightin one hour.

[0038] Once the subject hydrogel is blended as described in detail inthe above Examples, the hydrogel may be cast and molded in any size orshape but is preferably molded into ropes having a length ranging fromabout two to twelve inches but preferably between four to eight inchesand a width ranging from 0.1 to 2 inches but preferably about 0.25 to1.75 inches or into disks having a diameter ranging between one andtwelve inches but most preferably between two and six inches for ease ofuse. The thickness of the disks and ropes may vary substantially from0.01 to 1 inch in thickness but most preferably are molded to 0.1 inchto 0.75 inch in thickness for ease of use with acceptable absorption.

[0039] The unexpected significant advantages of the present hydrogeldressing achieved through the particular reaction ratios noted aboveinclude increased absorption capabilities and increased strength. Theincreased strength of the subject hydrogel material eliminates the needfor backing material as described in the prior art. Additionally, thehydrogel is stable, does not become brittle or crack with moisture loss,and has an extended shelf-life over other such materials.

[0040] The subject hydrogel dressing so produced is clear unless alteredby additives such as bacteriostatic or antimicrobial agents and thelike. Additive agents such as the silver salts will cause the resultinghydrogel dressing to discolor. The addition of other antibiotics,antifungals or organic additives either singularly or in combination mayresult in a less than desirable aesthetic appearance. Numerous organicdyes and inorganic pigments that are well known in the art may be addedto the hydrogel improving the appearance of the dressing withoutaffecting the function of the hydrogel.

[0041] After the hydrogel is cast, molded, and formed, which usuallytakes approximately one half hour to an hour at room temperature. Thegelatinization time can be shortened by curing the hydrogel at a highertemperature. The hydrogel once formed may be exposed to low temperaturessuch as below 0° C. for approximately one half to four hours butpreferably approximately one to two hours to extract excess water and tofully complete the reactions described above. This extraction of excessmoisture significantly and unexpectedly increases the absorptivecapabilities of the subject wound dressing which is capable of absorbingapproximately 2 to 6 times its weight.

[0042] The subject hydrogel dressing is packaged and sterilized using anappropriate sterilization technique or may be sterilized and thenpackaged using aseptic technique. Appropriate methods of sterilizationand packaging are known to those skilled in the art and include gammaradiation, electronic beam, ethylene oxide and like methods ofsterilization. Preferably, the subject hydrogel wound dressing ispackaged and then sterilized using gamma radiation by cobalt 60 with 1to 3 mrads but preferably 2 mrads in two independent exposure cycles.

[0043] Appropriate packaging for the subject hydrogel wound dressingincludes metallic foil pouches such as aluminum foil pouches,polyethylene film, ethylene vinyl acetate film, polypropylene film,polyvinyl chloride film, and like packages known to those skilled in theart.

[0044] The method of using the subject hydrogel wound dressing includesremoving the dressing from its packaging and placing the dressing on orin a wound. Depending on the amount of exudate draining from a woundsite, the dressing should be changed approximately every 1 to 2 days.The dressing in rope form can also be used for deep tunnel wounds. Thedressing may be cut using aseptic technique to a size appropriate for aparticular wound before placing the dressing on the wound. The dressingmay also be formed into various geometric shapes and packaged for anassortment of uses by the consumer. These geometric shapes may includecircular shapes that can be used by nursing mothers for the hydrogel'sabsorbent properties and additionally its cooling properties.

[0045] If after cutting the subject wound dressing the unused portionexperiences water loss, the same may be rehydrated using aseptictechnique and sterilized water.

[0046] It is seen therefore that the present hydrogel wound dressingprovides an effective moist wound dressing to maintain draining woundsin a clean protected state. The wound dressing and method of making andusing the same disclosed herein has specific advantages over theheretofore known means of treating draining wounds. The subject wounddressing eliminates risks associated with the treatment of drainingwounds, lessens tissue damage upon removal thereof and may be cut to theappropriate size for ease of placement and use. Hence, for these reasonsas well as others, some of which herein above set forth, it is seen thatthe present hydrogel wound dressing represents a significant advancementin the art which has substantial commercial significance.

[0047] Although the hydrogel material described in the illustrativeembodiment herein is utilized in the treatment of wounds having exudateit should be appreciated that hydrogel material could be implemented toabsorb bodily fluids that are not a result of a wound, such as milk froma lactating mother or urine in the incontinent patient, or the like. Itshould also be appreciated that the hydrogel can be used as a postoperative dressing in procedures where the healing incision wouldbenefit from a dressing having the properties of the hydrogel.Specifically, the hydrogel can be used as a post operative dressing forprocedures such as breast augmentation, mastectomy and rhinoplasty. Itcan also be effectively used as a dressing in the treatment of chronicwounds such as diabetic ulcers. Similarly, rather than utilize thehydrogel material for its absorbent qualities the hydrogel material canbe utilized for its ability to provide cooling properties to inflamedbody areas. Additionally, rather than utilize the hydrogel material forhuman use it can be utilized for various veterinary applications.Conversely, the hydrogel material can be used for non-medical uses andincorporated into sportswear, such as headbands and wristbands, for bothits absorptive and cooling properties.

[0048] While there is shown and described herein certain specificembodiments of the invention, it will be manifest to those skilled inthe art that various modifications may be made without departing fromthe spirit and scope of the underlying inventive concept and that thesame is not limited to the particular forms herein shown and describedexcept insofar as indicated by the scope of the appended claims.

What is claimed is:
 1. A hydrogel composition comprising from 5 to 30percent by weight of a polyurethane prepolymer, from 3 to 45 percent byweight of one or more alcohols selected from the group consisting ofpolyethylene glycol, polypropylene glycol and propylene glycol, and thebalance water, accelerator and an additive.
 2. The hydrogel compositionof claim 1 wherein said additive is an anti-microbial agent and is addedto reduce wound odor and risk of infection when used as a wounddressing.
 3. The hydrogel composition of claim 1 wherein said additiveis an anti-fungal agent and is added to reduce wound odor and risk offungal infection when used as a wound dressing.
 4. The hydrogelcomposition of claim 1 wherein said additive is an organic additiveagent and is added to reduce wound odor when used as a wound dressing.5. The hydrogel composition of claim 2 wherein said anti-microbial agentis selected from the group consisting of chorhexidene acetate,chlorhexideine gluconate, chlorhexidine hydrochloride, and chlorhexidinesulfate, silver acetate, silver benzoate, silvercarbonate, silveriodate, silver iodide, silver lactate, silver laurate, silver nitrate,silver oxide, silver palmitate, silver protein, and silver sulfadiazine,polymyxin, tetracycline, tobramycin, gentamicin, rifampician,bacitracin, neomycin, chloramphenical, oxolinic acid, norfloxacin,nalidix acid, pefloxacin, enoxacin, ciprofloxacin, ampicillin,amoxicillin, piracil, cephalosporins, vancomycin, and bismuthtribromophenate.
 6. The hydrogel composition of claim 5 wherein saidanti-microbial agents are in combination with other anti-microbialagents or other additives.
 7. The hydrogel composition of claim 3wherein said anti-fungal agent is selected from the group consisting ofTolnaftate, Miconazole, Fluconazole, Econazole, Ketoconazole,Itraconazole, Terbinafine, Amphotericin, Nystatin and Natamycin.
 8. Thehydrogel composition of claim 4 wherein said organic additive agent isselected from the group consisting of Grapefruit Seed Extract, Tea TreeOil, Myrtle Oil, and Lemon grass extract.
 9. The hydrogel composition ofclaim 1 wherein said hydrogel composition further includes a colorantsuch as an organic dye.
 10. The hydrogel composition of claim 1 whereinsaid hydrogel composition further includes a colorant such as aninorganic pigment.
 11. The hydrogel composition of claim 1 wherein saidadditive is a combination of an antimicobrial, an anti-fungal, and anorganic additive.
 12. A method of producing a hydrogel compositioncomprising: forming a first solution of polyurethane prepolymer andpolyethylene glycol; forming a second solution of water, propyleneglycol and accelerator; adding an additive agent to either said firstsolution or said second solution; and combining said first solution withsaid second solution.
 13. The method of claim 12 wherein said additiveagent is added to said first solution.
 14. The method of claim 12wherein said additive agent is added to said second solution.
 15. Themethod of claim 12 wherein said additive agent is an anti-microbialagent.
 16. The method of claim 12 wherein said additive agent is ananti-fungal agent.
 17. The method of claim 12 wherein said additiveagent is an organic compound.
 18. The method of claim 12 wherein saidcombined first and second solutions are cast, molded and heated.
 19. Themethod of claim 12 wherein said combined first and second solutions arecast and molded to form a wound dressing approximately 0.01 to 1.0 inchthick.
 20. The method of claim 12 wherein said combined first and secondsolutions are cast and molded to form a wound dressing in the shape of adisc with a diameter ranging from approximately 1.0 inch to 12.0 inches.21. The method of claim 12 wherein said combined first and secondsolution do not contain an additive.
 22. The method of claim 12 whereinsaid combined first and second solutions are cast and molded in theshape of a rope approximately 2 to 12 inches in length and 0.1 to 2.0inches in width.
 23. A hydrogel composition comprising a polyurethaneprepolymer, one or more alcohols selected from the group consisting ofpolyethylene glycol, polypropylene glycol and propylene glycol, and thebalance water, and an accelerator.
 24. The hydrogel composition of claim23 wherein said hydrogel composition is cast and molded to form adressing in the shape of a disc with a diameter ranging fromapproximately 1.0 inch to 12.0 inches.
 25. The hydrogel composition ofclaim 24 wherein said dressing is used as a nursing pad for lactatingmothers.
 26. The hydrogel composition of claim 23 wherein said hydrogelcomposition is cast and molded to form a dressing in the shape of a ropeapproximately 2 to 12 inches in length and 0.1 to 2.0 inches in width.27. The hydrogel composition of claim 26 wherein said dressing is usedas a post operative dressing for rhinoplasty.
 28. The hydrogelcomposition of claim 23 wherein said hydrogel composition is cast andmolded to form a dressing approximately 0.01 to 1.0 inch thick.
 29. Thehydrogel composition of claim 23 wherein said dressing is used as a postoperative dressing for mastectomy patients.
 30. The hydrogel compositionof claim 23 wherein said dressing is used as a pant liner forincontinent patients.